use field init shorthand EVERYWHERE

Like #43008 (f668999), but _much more aggressive_.

src/libpanic_unwind/gcc.rs

@@ -74,7 +74,7 @@ pub unsafe fn panic(data: Box<Any + Send>) -> u32 {
     let exception = Box::new(Exception {
         _uwe: uw::_Unwind_Exception {
             exception_class: rust_exception_class(),
-            exception_cleanup: exception_cleanup,
+            exception_cleanup,
             private: [0; uw::unwinder_private_data_size],
         },
         cause: Some(data),